1. Field of the Invention
This invention relates to a semiconductor device manufacturing method and a semiconductor device manufacturing apparatus, and more particularly a wafer dividing method and apparatus for dividing a wafer in which semiconductor elements have been formed, thereby forming semiconductor chips.
2. Description of the Related Art
In forming semiconductor chips by dividing a wafer in which semiconductor elements have been formed, for example, grooves or holes have been made in the surface of the wafer (or the semiconductor element formation face) by means of a diamond pen or the like and pressure has been applied mechanically, with each groove or hole as a starting point, thereby cleaving the wafer (refer to, for example, Jpn. Pat. Appln. KOKAI Publication No. 2000-124159, Jpn. Pat. Appln. KOKAI Publication No. 2001-257180, and Jpn. Pat. Appln. KOKAI Publication No. 2002-198326). Alternatively, a laser beam has been irradiated to form modified layers in the wafer and pressure has been applied mechanically, with each modified layer as a starting point, thereby cleaving the wafer (refer to, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-334675). Cleaving and dividing a wafer makes it possible to reduce the effect of chipping or cracking due to mechanical or thermal damage caused in dicing, which improves the strength of the semiconductor chips. As a result, when chips are made thinner, a decrease in the strength can be alleviated.
However, with such conventional dividing methods, it is difficult to optimize the external force at the time of cleaving. Since the application of more external force than necessary causes a semiconductor chip to crack or chip or the interference between semiconductor chips causes a crack or a chip, the shape of the cut surface cannot be made uniform, resulting in a decrease in the production yield. In the semiconductor device manufacturing method using the above dividing method, since cleaving is performed on a chip dividing line basis or a dicing line basis, the number of chips obtained from a single wafer increases as a result of the increase of the wafer size or the reduction of the chip size and therefore the time required to carry out the dividing step gets longer.